Using Relays to Control Multiple Solar Machines

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This page will show you how I wired the relays to my Arduino so that I can control more solar machines without having to build more driver boards. If you came to this page directly from a search engine, you might want to check out the heliostat projects page for an explanation for what the I’m talking about.

This circuit is meant to work in conjunction with the Arduino Stepper Motor Driver Board. Some of the components on that page are referenced here, so you might want to read it if you haven’t already.

Parts List

The parts list is pretty straight forward, and there isn’t a single component on it that can’t be swapped out for another similar part. The links below go to the exact parts I’m using. They don’t necessarily represent the perfect components so much as they just so happened to be what I had on hand.

Resistor http://www.alliedelec.com/search/productdetail.aspx?SKU=2964741
Resistor; Carbon Film; Res 1 Kilohms; Pwr-Rtg 0.25 W; Tol 5%; Axial; Cer-Core

Diode http://www.alliedelec.com/search/productdetail.aspx?SKU=2660003
DIODE; 1 A (MAX.) @ 25C IF; 1.1 V (MAX.) @ 25C; 5 UADC (MAX.) @ 25C IR

Transistor http://www.alliedelec.com/search/productdetail.aspx?SKU=2482066
TRANSISTOR, POWER; NPN; 100VCE; 100VCB; 5VEB; 3A ICC; 1A IB; 40 W @ <= 25 C

Relay I don’t have the link for the relay, but most any should do as long as it can be powered by your stepper motor’s power supply.

Protoboard You can use any protoboard that’s left over from when you made the driver board to mount the relay on.

Schematic

Here is the schematic for the relay circuit.  All it does is essentially turn the power on and off for two stepper motors.

For every solar machine you want to control, you will need to add another one of these circuits. (Click for Bigger Picture)

To power on a pair of stepper motors, a shift register pin (or just an Arduino pin if you don’t need the extra outputs) is turned on inside the Arduino sketch. That signal turns on a transistor and the transistor turns on a relay. Current is then able to flow from the motor’s power supply to one pair of stepper motors.

Transistor

Here is a picture showing which leads are which for the transistor in the above schematic. The smaller sized transistors use a different ordering for the base, collector, and emitter. Something to keep in mind if you were to try and modify the schematic.

Pictures of the Build

Here are some pictures from when I assembled one of my Arduino controlled relays. This first one shows all the various parts laid out and ready for assembly.

Here’s a quick shot of the resistor, transistor, and diode after being set in the protoboard.

This next pic shows the installed relay and attached wires. From top to bottom, the first wire goes out to the shift register (or Arduino) pin, the second goes to ground (-), the third goes out to the positive wire on the motors power supply, and the last wire goes out to the altitude and azimuth stepper motors.

Here is a quick shot of the bottom.

I made several of these circuits. Each one allows me to control another solar machine.

Here is one final picture of it being installed and tested. It works!

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